MECHANOCHEMICAL TRANSDUCTION IN MUSCLE

这些研究的总体目标是定量描述各种 哺乳动物平滑肌和骨骼肌中需要能量的反应，以及 希望能找出一些控制能量转化率的因素 不同工艺的使用。 骨骼肌能量学实验 将确定能量的不稳定部分是否 由于预刺激而产生的使用可以被分配到力依赖的 和/或力独立过程。 计划在骨骼肌方面开展的其他工作 将处理跨桥循环速率的测量（从Vmax 在等长性破伤风期间的不同时间， 确定预刺激对时间依赖性 单次破伤风中Vmax的变化。 实验的基本原理是 将能量学数据与跨桥的独立测量数据合并， 循环率，以便对引起 可以在不同的条件下获得总的高能磷酸盐使用量 机械条件。 这些实验将包括Vmax测试 完整肌肉在不同代谢状态下的变化。 我们之前的工作 表明肌球蛋白的程度与肌球蛋白的水平之间没有一致的关系， 轻链磷酸化和高能磷酸平均速率 在兔结肠带中的用途。 我们目前正在扩大这些研究 包括所有条件下最大缩短速度的测量， 在这种情况下，我们有能量和肌球蛋白轻链 磷酸化数据。 这些实验将严格检验 肌球蛋白轻链磷酸化控制交叉桥假说 循环速率，但不是哺乳动物平滑肌的力输出。 进一步 刚刚开始的关于监管的实验， 平滑肌收缩涉及力学和肌球蛋白光测量 雪貂门静脉等长强直时链磷酸化。 选择这种组织是因为它最近被用来测量钙 与Ca+2-敏感蛋白水母发光蛋白的瞬变。 已经发现 钙瞬变是完全不同的， 与钾去极化相比， 一 该组织中完整的机械和轻链磷酸化研究 应阐明游离细胞质钙浓度是否起作用 不依赖于肌球蛋白轻链调节完整平滑肌 磷酸化

The overall goal of these studies is to describe quantitatively the various energy requiring reactions in mammalian smooth and skeletal muscle, and hopefully to identify some of the factors which control the rate of energy usage by the different processes. Skeletal muscle energetics experiments will be done to determine whether or not the labile portion of the energy usage due to prestimulation can be apportioned into a force dependent and/or a force independent process. Other work planned on skeletal muscle will deal with measurement of the crossbridge cycling rate (from Vmax determinations) at different times during an isometric tetanus, and will determine the effect, if any, of prestimulation on the time dependent changes in Vmax in a single tetanus. The rationale for the experiments is to merge the energetics data with an independent measurement of crossbridge cycling rate so that a coherent description of the factors giving rise to the total high energy phosphate usage can be obtained under different mechanical conditions. Included in these experiments will be tests of Vmax of the intact muscle in different metabolic states. Our previous work has shown that there is no consistent relationship between the degree of myosin light chain phosphorylation and the average rate of high energy phosphate usage in the rabbit taenia coli. We are presently extending these studies to include measurements of maximum shortening velocity under all of the conditions in which we have energetics and myosin light chain phosphorylation data. These experiments will critically test the hypothesis that myosin light chain phosphorylation controls crossbridge cycling rate, but not force output of mammalian smooth muscle. Further experiments which have just been initiated concerning the regulation of smooth muscle contraction involve measurement of mechanics and myosin light chain phosphorylation during isometric tetani in the ferret portal vein. This tissue was chosen since it has recently been used to measure calcium transients with the Ca+2-sensitive protein aequorin. It has been found that the calcium transients are quite different when the tissue is activated with phenylephrine compared to potassium depolarization. A complete mechanical and light chain phosphorylation study in this tissue should clarify whether free cytoplasmic calcium concentration plays a role in regulation of intact smooth muscle independently of myosin light chain phosphorylation.